This is an interesting epidemiological finding. A reproduction of this association in other populations would be needed. Of note, one of the autoantigens of type I diabetes (GAD, glutamic acid decarboxylase) is expressed in the nervous system and autoantibodies against GAD lead to a rare neurological disorder, Stiff-Person-Syndrome. Immunologically, type I diabetes is very complex, involving cellular and humoral immune effector mechanisms. How this may protect against the development of schizophrenia is not easily explained.